Motor-Generator Systems

Abstract

A motor-generator system comprises: an internal combustion engine; a motor-generator drivingly engaged with the internal combustion engine via an endless belt; a controller detecting a speed signal of the internal combustion engine, a driver input signal, a battery status signal, and a motor-generator signal; the motor-generator being operable to provide an electric drive torque or a load torque to the internal combustion engine at a predetermined frequency according to a controller instruction; and the controller controlling the motor-generator torque at a frequency greater than 1 Hz, so that when the internal combustion engine accelerates, the electric drive torque is applied to accelerate the rotation of the motor-generator, and when the internal combustion engine decelerates, the load torque is applied to decelerate the rotation of the motor-generator, so that the rotation of the motor-generator is controlled to reduce system vibration.

Description

[0001] This application is a divisional application of the invention patent application named “Motor-Generator System”, with an international application date of March 5, 2018, an international application number of PCT / US2018 / 020916, and a national application number of 201880016298.1. Technical Field

[0002] The present invention relates to a motor-generator system, and more specifically, to a controller that controls the torque of the motor-generator at a frequency greater than 1 Hz, so that when an internal combustion engine accelerates, an electric drive torque is applied to accelerate the rotation of the motor-generator, and when the internal combustion engine decelerates, a load torque is applied to decelerate the rotation of the motor-generator, so that the rotation of the motor-generator is controlled to reduce system vibration. Background Art

[0003] An internal combustion engine burns an air / fuel mixture to drive a piston, which rotatably turns a crankshaft to generate a drive torque. The drive torque is transmitted from the crankshaft to the drivetrain to propel the vehicle. An electric motor can be used to temporarily power a mild hybrid vehicle, which allows the engine to be periodically shut down to reduce fuel consumption. An example of a mild hybrid vehicle is a vehicle with an engine and a belt-driven starter generator (BSG). The crankshaft of the engine is coupled to the crankshaft pulley, and the BSG is coupled to the crankshaft pulley via a belt. When the engine needs to be restarted after a period of inactivity, the BSG can use the belt to rotate the crankshaft to quickly and smoothly restart the engine.

[0004] Multi-ribbed belts are commonly used on motor vehicles to transfer power between the engine and auxiliary components. On conventional drive arrangements, the engine crankshaft pulley drives the accessories via one or more belts. When multiple accessories are driven via belts, a tensioner is usually used.

[0005] In recent years, motor-generator units (MGUs) have been implemented to perform BSG engine start-stop to provide torque to assist in engine acceleration, as well as recuperation to generate electricity in addition to the normal power generation usually performed by the alternator. BSG can achieve significant fuel savings and reductions in exhaust gases.

[0006] In order to control the tension in two different modes: electric drive mode (MGU drive) and power generation mode (engine drive), a set of tensioners is often designed for BSG drive devices. The common feature of the designs is that the tensioner has two arms connected by a spring. These tensioners can control the belt tension in both modes (electric drive mode and power generation mode). Since the movement of the two arms is coupled via a spring, the first frequency of the system is significantly reduced, which is usually lower than the engine ignition frequency at idle speed, and the vibration of the belt drive device is significantly reduced in the normal operating speed range.

[0007] However, during engine key starting, when the engine speed ignition frequency passes through the reduced system frequency, belt drives using this type of tensioner exhibit high system vibrations, creating system resonances associated with NVH issues. To attenuate system vibrations for belt drives using MGUs, special control of the MGU torque is required to control MGU motion.

[0008] The BSG drive can be implemented independently to become a mild hybrid system, or operate as a hybrid system with an integrated starter generator system (ISG). When the driver accelerates to accelerate the vehicle, the MGU in the BSG drive generates drive torque, which consumes power from the battery to start the engine or boost engine acceleration. The MGU also acts as an alternator or generator, applying load torque to generate electricity to charge the battery: recuperation or normal power generation. Recuperation generates high torque loads typically seen in braking operations as well as high power and generates moderate loads when the driver's foot is off the pedal.

[0009] In driving or generating mode, the amount of torque from the MGU is controlled by several factors. For example, higher driving torque in acceleration operation when the driver accelerates very hard; or higher load torque in regeneration operation when the driver needs to brake hard. There is a common feature: the direction of the torque (driving or loading) from the MGU does not change until the driver changes the operating requirements of the engine.

[0010] The rotational speed of an internal combustion engine fluctuates around its average speed. Fluctuations in engine speed are called angular vibrations (AV). For example, a 4-cylinder engine running at an average speed of 750 rpm can have an AV of 60 rpm at an ignition frequency of 25 Hz. For the proper control of a BSG drive, the engine average speed is the main factor. The engine / vehicle acceleration / deceleration refers to the average speed.

[0011] Prior art BSG systems are used for torque boost, where the BSG provides starting torque or additional drive torque to supplement the torque output of the IC engine.

[0012] Representative of this field is U.S. Patent 9,303,571, which discloses a method for determining a desired torque output from an engine system in response to a torque request, the engine system comprising an engine and a belt-driven starter generator (BSG). The method may include determining a current engine torque capacity. When the desired torque output is greater than the current engine torque capacity, the method may include (i) determining a maximum engine torque capacity, (ii) determining a current BSG torque capacity, (iii) commanding the BSG to operate as a torque generator or a torque consumer based on the difference between the desired torque output and the maximum engine torque capacity and based on the state of a battery system configured to power the BSG, and (iv) controlling the engine and the BSG to cooperatively generate the desired torque output at the flywheel of the engine.

[0013] What is needed is a controller that controls the motor-generator torque at a frequency greater than 1 Hz so that when an internal combustion engine accelerates, an electric drive torque is applied to accelerate the rotation of the motor-generator, and when the internal combustion engine decelerates, a load torque is applied to decelerate the rotation of the motor-generator so that the rotation of the motor-generator is controlled to reduce system vibration. The present invention meets this need. Summary of the invention

[0014] A main aspect of the present invention is to provide a controller that controls the motor-generator torque at a frequency greater than 1 Hz, so that when the internal combustion engine accelerates, an electric drive torque is applied to accelerate the rotation of the motor-generator, and when the internal combustion engine decelerates, a load torque is applied to decelerate the rotation of the motor-generator, so that the rotation of the motor-generator is controlled to reduce system vibration.

[0015] Other aspects of the invention will be pointed out or will be apparent from the following description of the invention and the accompanying drawings.

[0016] The present invention includes an electric motor-generator system, which includes: an internal combustion engine; an electric motor-generator, which is drivingly engaged with the internal combustion engine through an endless belt and an electric motor-generator; a controller, which detects a speed signal of the internal combustion engine, a driver input signal, a battery status signal, and a electric motor-generator signal; the electric motor-generator is operable to provide an electric drive torque or a load torque to the internal combustion engine at a predetermined frequency according to an instruction of the controller; and the controller controls the torque of the electric motor-generator at a frequency greater than 1 Hz, so that when the internal combustion engine accelerates, an electric drive torque is applied to accelerate the rotation of the electric motor-generator, and when the internal combustion engine decelerates, a load torque is applied to decelerate the rotation of the electric motor-generator, so that the rotation of the electric motor-generator is controlled to reduce system vibration. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate preferred embodiments of the present invention and, together with the description, serve to explain the principles of the present invention.

[0018] Figure 1 Schematic diagram of the BSG system.

[0019] Figure 2 It is a control schematic diagram.

[0020] Figure 3 A tensioner for the connection.

[0021] Figure 4a This is the system vibration diagram.

[0022] Figure 4b This is a diagram of system frequency.

[0023] Figure 4c A schematic diagram of the system.

[0024] Figure 4d A schematic diagram of the system.

[0025] Figure 4e A schematic diagram of the system.

[0026] Figure 4f A schematic diagram of the system.

[0027] Figure 5a is a graph showing the crankshaft rotation speed during engine starting.

[0028] Figure 5b is a diagram showing the movement of the base arm of the tensioner during engine starting.

[0029] Figure 5c is a diagram showing the movement of the tensioner side arm during engine starting.

[0030] Figure 6 is a graph showing MGU engine speed and fluctuations during engine starting.

[0031] Figure 7 This is the MGU control flow chart.

[0032] Figure 8 is a graph showing the relationship between MGU torque and time.

[0033] Fig. 9 A diagram showing the movement of the tensioner arm. DETAILED DESCRIPTION

[0034] Reference now Figure 1 , showing an example diagram of an engine system 100. The engine system 100 includes an internal combustion engine 104 (hereinafter referred to as "engine 104"). The engine 104 can be any suitable engine (spark ignition engine, diesel engine, homogeneous charge compression ignition engine, etc.) configured to combust an air / fuel mixture to generate drive torque. The fuel can be gasoline, diesel, or other suitable combustible fuel (ethanol, natural gas, propane, hydrogen, etc.). The engine system 100 can be implemented in a vehicle, and the drive torque generated by the engine 104 is used to propel the vehicle using transmission components and suitable transmission system components.

[0035] The engine 104 draws air into an intake manifold 108 through an intake system 112 regulated by a throttle 116. The air in the intake manifold 108 is distributed to a plurality of cylinders 120 and combined with fuel (e.g., gasoline) from a fuel injector (not shown) to produce an air / fuel mixture. The engine 104 may include any number of cylinders. The air / fuel mixture is compressed and combusted in the cylinder 120 to drive a piston (not shown) that rotatably rotates a crankshaft 128 to generate a drive torque. An ignition controller (IC) 124 controls the timing of the combustion of the air / fuel mixture, e.g., the timing of a spark plug. The drive torque is transmitted from the crankshaft 128 to the drivetrain components of the vehicle.

[0036] The engine system 100 includes a motor-generator unit (MGU) 136. The MGU 136 is coupled to the crankshaft 128 via a belt 140, through a shaft 153. The shaft 153 includes a pulley (not shown) that engages the belt 140. The drive torque is partially transmitted to the MGU 136 via the belt 140, wherein the MGU 136 operates as a "torque consumer." Similarly, in another operating mode, the MGU 136 drives the crankshaft 128 via the belt 140, for example, during engine restart or acceleration. In this mode, the MGU is a "torque generator." The MGU 136 can be powered by a battery system 144. The battery system 144 can include a single battery, such as a typical 12 volt lead-acid automotive battery, or the battery system can include a battery pack including a plurality of batteries, such as a 48 volt lithium-ion battery pack. The tensioner 400 engages the belt 140 via pulleys 401 and 402, see Figure 3 The tensioner 400 applies a belt load to the belt 140 so as to maintain appropriate tension in the belt 140 , whereby power is transmitted from the crankshaft 128 to various driven accessories.

[0037] The MGU 136 includes an electric motor (EM) 148 and an alternator (ALT) 152. When the MGU 136 drives the crankshaft 128, the electric motor 148 is powered by the battery system 144. Therefore, the ability of the MGU 136 to operate as a torque generator depends on the state of the battery system 144. For example, when the state of charge (SOC) of the battery system 144 is below a predetermined threshold, the MGU 136 can be prohibited from operating as a torque generator. Alternatively, when the MGU 136 is driven by the crankshaft 128, the MGU generates current used to recharge the battery system 144.

[0038] The engine 104 generates a desired torque based on a driver input via a driver input device 156 (e.g., an accelerator pedal). The driver input may represent a torque request for the engine system 100. The controller 160 controls the operation of the engine system 100, and more specifically, the components of the engine system 100 to meet the torque request. The controller 160 controls airflow by controlling the throttle 116 and controls ignition timing by controlling the ignition controller 124. The controller 160 also controls the MGU 136 by selectively powering the motor 148 according to a specific duty cycle and using current from the battery system 144, which will be described in more detail below.

[0039] Reference now Figure 2, showing an exemplary functional block diagram of the controller 160. The controller 160 includes a communication device 200, a processor 204, and a memory 208. The memory 208 may include any suitable storage medium configured to store code and information for the controller 160. For example, the memory 208 may store a predetermined threshold value (multiple predetermined threshold values) for the battery system 144 and / or the MGU torque coefficient, which will be described in more detail below.

[0040] The controller 160 detects a speed signal of the internal combustion engine 104 , a driver input signal 156 , a battery status signal 144 , a motor-generator status signal 136 , and a throttle position signal 116 .

[0041] The communication device 200 may include any suitable component (e.g., a transceiver) configured to communicate with components of the engine system 100 (throttle 116, ignition controller 124, MGU 136, battery system 144, driver input device 156, etc.) via a controller area network (CAN). It should be understood that the communication device 200 may also be configured to communicate with other components (remote server, mobile phone, another vehicle, etc.) via another network (such as a local area network (LAN), such as Bluetooth communication; or a wide area network (WAN), such as the Internet).

[0042] The processor 204 is configured to control the operation of the controller 160. Functions may include, but are not limited to, loading / executing an operating system of the controller 160, controlling information sent via the communication device 200, processing information received via the communication device 200, and controlling read / write operations at the memory 208. The processor 204 may also perform torque management techniques in whole or in part.

[0043] The processor 204 determines the desired torque output (T 所需 ). The torque request may be based on a driver input via the driver input device 156. The desired torque output from the engine system 100 represents the desired torque of the engine 104 at the crankshaft 128. The torque at the crankshaft 128 may be provided by the engine 104 or a combination of the engine 104 and the MGU 136 operating as a torque generator.

[0044] Processor 204 may determine the current engine torque capacity (ET 当前 The current engine torque capacity represents the torque capacity of the engine 104 under current operating parameters (driver input, throttle position, ignition timing, etc.).

[0045] The processor 204 then determines whether the desired torque output of the engine system 100 is greater than the current engine torque capacity. When the desired torque output of the engine system 100 is less than or equal to the current engine torque capacity, the processor 204 controls the engine 104 via the communication device 200 to generate the desired torque output at the flywheel 132. When the desired torque output is greater than the current engine torque capacity, the processor 204 determines the maximum engine torque capacity. The maximum engine torque capacity represents the maximum torque capacity of the engine 104 under any operating conditions. The processor 204 determines the current MGU torque capacity. The current MGU torque capacity includes the torque capacity of the MGU 136 under the current operating conditions.

[0046] The processor 204 commands the MGU 136 to operate as a torque generator or a torque consumer via the communication device 200 based on (i) the difference between the required torque output of the engine system 100 and the maximum engine torque capacity and based on (ii) the state of charge of the battery system 144. When the state of charge of the battery system 144 indicates that the MGU 136 will not be able to operate as a torque generator to generate torque at the crankshaft 128, the processor 204 commands the MGU 136 to operate as a torque consumer (torque load). Similarly, when the state of the battery system 144 indicates that the MGU 136 will be able to operate as a torque generator to generate torque at the crankshaft 128 within a suitable period of time, the processor 204 can command the MGU 136 to operate as a torque generator. There may also be such states of the battery system 144 in which the MGU 136 can operate as a torque generator or a torque consumer.

[0047] After determining whether to operate the MGU 136 as a torque generator or a torque consumer, the processor 204 controls the engine 104 and the MGU 136 via the communication device 200 to cooperatively generate the desired torque output at the flywheel 132 of the engine 104. In some cases, the MGU 136 may be able to generate sufficient torque at the flywheel 132 so that the engine 104 can continue to operate at the current operating parameters (throttle position, ignition timing, etc.). In other cases, if necessary, the processor 204 can adjust the operating parameters of the engine 104 to increase the torque output of the engine at the flywheel 132 up to the maximum engine torque capacity. More specifically, the processor 204 can control the engine 104 via the communication device 200 to generate the sum of (i) the desired torque output and (ii) a portion of the current MGU torque capacity at the flywheel 132 when the MGU 136 is commanded to operate as a torque consumer. Alternatively, processor 204 may control engine 104 via communication device 200 to generate the difference between (i) the desired torque output and (ii) a portion of the current MGU torque capacity when MGU 136 is commanded to operate as a torque generator.

[0048] Figure 3 The coupled tensioner 400 is typically implemented for use with an MGU drive. The coupled tensioner is typically fixed to the MGU 136 and engages the belt 140, see Figure 4f . A coupled tensioner (also referred to as a track tensioner) typically includes a dual arm single spring function. Base arm 401a rotates about base 403. Side arm 402a pivots on base arm 401a. Base arm 401a and side arm 402a are biased to apply belt load using torsion springs (not shown). Each pulley 401, 402 engages a section of belt 140 to maintain proper tension in belt 140. Shaft 153 of MGU 136 protrudes through a center portion of tensioner 400. Belt 140 engages a pulley (not shown) mounted to shaft 153.

[0049] The first natural frequency of the belt drive is significantly lower than the natural frequency of a lock-center drive or a single tensioner. Figure 4a As shown in , with the coupled (CPL) tensioner, the first system frequency is reduced to 11 Hz. The first system frequency is usually much lower than the engine firing frequency at engine idle. For example, the firing frequency of a 3 cylinder engine at 800 rpm is 20 Hz. For a 4 cylinder engine firing at 800 rpm, the frequency is 26.7 Hz. Therefore, the main system resonance does not occur in the normal engine speed range.

[0050] However, during engine starting, whether during key start or low speed MGU starting, the engine begins to fire at a speed below the resonant speed. As a result, when the engine speed passes the resonant speed, there will be system resonance, resulting in excessive system vibration.

[0051] Figure 4b is a graph showing the first system frequency of different types of tensioners. "Fixed" refers to Figure 4c The fixed idler wheels A and B are shown in FIG. Figure 4c In the embodiment, the crankshaft pulley 500 is engaged with the auxiliary pulley 600 and the MGU rotor pulley 175 via the belt 140. "Single tensioning" refers to the Figure 4d The single arm tensioner shown in the figure. "Dual tensioner" refers to the Figure 4e Two separate tensioners shown in .

[0052] "CPL tensioning" means Figure 4f The coupled tensioner 400 is schematically shown in FIG. Figure 3 A coupled tensioner 400 is described in . Each arm of the tensioner 400 engages band segments B1 and B2 . The tensioner 400 is mounted to the MGU 136 .

[0053] Shown in FIG. 5 are the engine speed and tensioner arm vibrations measured during a key start of a 4-cylinder diesel engine equipped with a dual mass flywheel. Figure 5a The crankshaft rotation speed is shown. Figure 5b The angle of the tensioner base arm 401a is shown versus time. Figure 5c The angle of the tensioner side arm 402a is shown versus time.

[0054] The MGU drive with the attached tensioner resonated around 400 rpm. The attached tensioner base arm had a peak-to-peak vibration of 55°, and the side arm had a peak-to-peak vibration of 40°; both exceeded the design limit for durability. Peak belt tension and hub loads were also above allowable limits.

[0055] Excessive system vibrations are attributed to 1) high engine speed fluctuations or angular vibrations and 2) high effective moments of inertia of the MGU, and 3) engine speeds near system resonance frequencies. In the case of engine starting, the vibration is the first system resonance.

[0056] Since the MGU rotor motion and its inertia torque are the main factors that make the system dynamic characteristics too large, the purpose is to use the MGU torque to rotate the MGU rotor according to the engine speed. That is, when the engine is accelerating, the electric drive torque is applied to accelerate the MGU rotor. When the engine is decelerating, the load torque is applied to decelerate the MGU rotor. These MGU actions for vibration reduction are applicable not only to engine starting, but also to other engine operations when the MGU drive device has vibration problems.

[0057] refer to Figure 6 , which shows the relationship between MGU rotor speed and time, in order to achieve vibration damping (attenuation) via MGU torque control, the engine speed is measured and the required MGU acceleration / deceleration is calculated. The MGU torque is applied according to the inertia torque calculated by the MGU acceleration / deceleration, which is considered to be (CRK acceleration / deceleration × speed ratio × inertia of MGU rotor). For example, for CRK acceleration = 20,000rpm / s or 2094rad / s^2, a speed ratio of 2.6, and an MGU rotor inertia of 0.0045kg-m^2, the inertia torque of the MGU rotor is 24.5Nm.

[0058] The MGU torque is controlled as follows:

[0059] 1) No action is taken when the MGU inertia torque is less than the required threshold torque (TQ); +TQ during acceleration (usually clockwise as the engine rotation direction) and -TQ during deceleration (counterclockwise).

[0060] 2) When the inertia torque reaches or exceeds the threshold value TQ, the MGU torque is applied by the MGU as a constant or variable torque. It is applied as an electric drive torque or drive torque during acceleration and as a load torque during deceleration.

[0061] Figure 7 , which is a flow chart of MGU torque control. First, the engine speed and the MGU speed are measured (201). The speed ratio of the MGU speed and the engine speed is calculated by the controller (202). Then, the appropriate MGU acceleration / deceleration is calculated by the controller (203). Then, the MGU inertia torque is calculated by the controller (205). If the inertia torque is greater than the threshold torque (206), the MGU applies a driving torque (208) according to the command of the controller. If the inertia torque is less than the threshold torque (207), the MGU applies a load torque (209) according to the command of the controller.

[0062] Figure 8 An example of MGU torque during engine starting is shown in . The graph shows the MGU torque in Nm as a function of time.

[0063] Fig. 9 An example of tensioner arm vibration reduced by MGU torque action is shown in FIG. Specifically, vibration of base arm 401a is reduced by 29%, and vibration of side arm 402a is reduced by 54%. MGU torque action adjustments are applied to the system by the controller at a frequency greater than about 1 Hz. For example, in Fig. 9 In the example, the frequency is about 18 Hz, which is greater than 10 Hz. The MGU torque action frequency is less than about 50 Hz because vibration reduction is most needed at engine start-up when the RPM is low.

[0064] A motor-generator system comprises: an internal combustion engine; a motor-generator drivingly engaged with the internal combustion engine via an endless belt and the motor-generator; a controller detecting a speed signal of the internal combustion engine, a driver input signal, a battery status signal and a motor-generator signal; the motor-generator being operable to provide an electric drive torque or a load torque to the internal combustion engine at a predetermined frequency according to a controller instruction; and the controller controlling the motor-generator torque at a frequency greater than 1 Hz, so that when the internal combustion engine accelerates, the electric drive torque is applied to accelerate the rotation of the motor-generator, and when the internal combustion engine decelerates, the load torque is applied to decelerate the rotation of the motor-generator, so that the rotation of the motor-generator is controlled to reduce system vibration.

[0065] Although forms of the invention have been described herein, it will be apparent to those skilled in the art that changes may be made in the construction and relationship of parts without departing from the spirit and scope of the invention described herein.

Claims

1. A method for controlling the torque of a motor-generator, the method comprising: Measuring engine speed; Detecting acceleration or deceleration of a motor-generator; calculating the inertia torque of the motor-generator using the acceleration or deceleration; determining a threshold torque; determining whether the inertia torque of the motor-generator is greater than or less than the threshold torque; If the inertia torque of the motor-generator is greater than the threshold torque, applying a drive torque to the motor-generator to dampen system vibration; If the inertia torque of the motor-generator is less than the threshold torque, applying a load torque to the motor-generator to dampen system vibration; and The drive torque and the load torque are applied at a frequency in the range of 1 Hz to 50 Hz.

2. The method according to claim 1, wherein: Applying the drive torque and the load torque is performed at a frequency of less than 30 Hz. 3 . The method of claim 1 , comprising applying the drive torque and load torque for an engine speed less than 1000 RPM.

4. A method of controlling a motor-generator system, the method comprising: Measuring engine speed; coupling a motor-generator to the engine with a belt; calculating the inertia torque of the motor-generator; determining a threshold torque of the motor-generator based on the engine speed; determining whether the inertia torque of the motor-generator is greater than or less than a threshold torque of the motor-generator; The inertia torque of the motor-generator is controlled for engine speeds less than 1000 RPM and load torque or drive torque is applied at a frequency greater than 1 Hz to damp system vibrations. 5 . The method of claim 4 , comprising controlling the inertia torque of the motor-generator for engine speeds greater than 100 RPM.

6. The method of claim 4, comprising controlling the inertia torque of the motor-generator to dampen system vibrations by applying a load torque or a drive torque at a frequency less than 50 Hz.

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